Mark Duplass discovered how damaging spoilers can be when he went to see “The Crying Game” at age 14.

“It took me like two weeks to get to the theater, so I had held off [knowing] everything,” says the 37-year-old star of “The One I Love” at the James Hotel. “Literally right as the lights went down, the woman in front of me leaned over to her husband and was just like—and I’m not going to say it here for people who haven’t seen it—but was like, ‘Don’t worry, when this happens, it’s not that graphic.’ And I was like, ‘Un[bleep]ingbelievable! I’ve been trying to hold this for two weeks!’”

“The One I Love,” opening Friday, doesn’t have a twist of “Crying Game” proportions. But Duplass (who’s married to his “The League” costar Katie Aselton) and 31-year-old, first-time feature director Charlie McDowell (son of Malcolm McDowell) are smart to want viewers to experience the unusual, insightful romantic drama without knowing too much beforehand. The basics: Ethan (Duplass) and Sophie (Elisabeth Moss) go to a retreat recommended by their therapist (Ted Danson, McDowell’s stepdad) to repair their marriage and discover something very unexpected.

By the way, Duplass (recently in “Tammy” and “The Mindy Project”) didn’t speak up to the woman who ruined “The Crying Game”: “I was 14. I was scared of adults.”

“The One I Love” addresses the issue of allegedly presenting the best version of yourself at the beginning of a relationship. To what extent can first dates be seen as a degree of false advertising?

Mark Duplass: In my experience they are usually that way. To a large degree.

MD: There are occasionally these couples that you meet that they’re like, “Oh, we were friends for like five years, and then we got together.” And I’m like, “I think that might be the way to do it.” You kind of sneak in there without any of the faking going on. When I met my wife Katie, it was through friends of friends and it was on New Year’s Eve, and I had just kind of had a mutual breakup with this girl a couple of months before, and [Katie] was asking me about it. And I remember in my head as I was telling it to her, I was like, “Why am I lying about this? Why am I lying about this?” But I was doing it!

And I told her this story about, “Look, I just knew I wasn’t ever going to be truly attracted to her in the way that it needed to happen, so I just looked her in the eye. I just told her exactly what I felt. I was really honest with her about it.” It was not at all that way! I lied. I was backhanded about it. But she thought it was the coolest thing, and I remember her telling me that like a year later, “I just loved that story.” And I was like, “It kinda didn’t happen that way.”

How would it work out if people were super upfront, even on the first date?

MD: Are we talking bathroom-with-the-door-open kind of thing?

Maybe not that upfront.

CMcD: I can’t tell if more people would be together or less people would be together. It’s something we’re all conditioned to do is look at someone—I think you do it with friends, you do it with how you communicate with people, you sort of adapt.

MD: You do it at parties.

CMcD: Yeah, you adapt to who they are. If someone’s really shy, then for me I like become the guy who’s super-chatty and talky. And if someone’s super-chatty and talky, I literally shut down. I think it’s a lot of adapting to what you’re getting from other people.

Can you put these elements in order in terms of what you think is most important in a relationship: trust, communication and having fun together?

MD: I wouldn’t use those three in particular. For me it’s a very subjective thing. The most important thing for me at this stage is people who are emotionally aware and that they know when they’re being insecure, they know when they’re being an asshole, they know when they’re being certain ways so that you can have good conversations about that. I personally don’t believe that you can be in a long-term relationship with someone who doesn’t know themselves and have the ability to laugh at themselves. It’s a killer in my opinion.

CMcD: Yeah, I definitely agree with that.

MD: Great butt, also.

CMcD: Yeah. Something that you said is for me communication is a huge one. Especially being in this business, there’s constantly traveling and moving around, and the idea is it’s hard to be on the same page when you’re not in the same place. The biggest one in my relationship is just communication.

In the movie, Ethan mentions to Sophie a fun memory of them doing X at Lollapalooza. Whose personal experience did that come from?

MD: I didn’t do X at Lollapalooza, but in 1992 me and my friends got really stoned and went to Lollapalooza to see Soundgarden and Pearl Jam. And then just yelled at the stage the entire time for them to get together and do Temple of the Dog.

And did they?

MD: They did not! No, they did not at all. But it was a hell of a show. That was in New Orleans, where I grew up.

Charlie, we heard a movie that was spoiled for Mark. Did you have one?

CMcD: One thing that happened-—it’s actually funny because we both know the person that said it—I’m really into “Game of Thrones” right now. I just got caught up.

MD: I’m not caught up. Shhh.

CMcD: A mutual friend of ours—[to Duplass] I’ll tell you the story later—made a reference to something that he thought was the end of Season 2, which was where I was, but it was the end of Season 3. I didn’t know what it meant but—

MD: I know who this friend was because he did it to me this weekend. Again! He just did it to me.

CMcD: Who?

MD: He’s very tall.

CMcD: [Laughs.] Yeah. He made a reference that the whole season I was like, “He must have screwed up because it didn’t happen in—” And then right in the moment I was like, “Oh my God, this is what it is.” And I realized it 10 seconds before, and if I hadn’t known anything it truly would have blown my mind.

MD: He only got half a blown mind.

CMcD: So that was a spoiler. But I think with our film we truly believe the best way to see the movie is to not know anything. We think that that’s the best experience, so we’ve used that as part of our marketing campaign and our idea. It’s not just to be cute.

MD: I kind of [did it to be cute].

I think all movies are better that way.

MD: Yeah, the hard truth of this is there’s a hardcore group of cinephiles, our reviewers, and our film buyers and our festival programmers and a lovely section of the public that will go see those movies because it’s well reviewed, because it was at Sundance or South By, but then how do you get to the rest of those people? That is why people do spoilers, and I understand it, and I’m OK with it on certain movies, but it wasn’t right for this one.

Charlie, how much do the girls that live above you know how much they helped you out with the Twitter feed/book, “Dear Girls Above Me”?

CMcD: I don’t live at that apartment anymore--I have it as an office so it’s there, but I don’t have to listen to them 24/7. As far as I know they’re still just chatting away.

MD: It makes me feel like the end of “Grease” where they ride the car off into the sky. They’re just chatting away …

CMcD: As far as I know they don’t know. I used different names and things, so the only way they would have found out is through seeing my face on Twitter and making the connection or just seeing stuff that they had said.

CMcD: When I lived there, I was really terrified. I started getting nightmares and anxiety about it, but since then I haven’t just ‘cause I haven’t been living there.

Plus:

On Chicago: “I shot a movie called ‘Hannah Takes the Stairs’ here in 2005, I think. I love the concept of a beach on a lake. ‘It’s so great that I’m in sand, but I’m not getting destroyed by waves and I can just go out a hundred yards and swim without a shark maybe getting me.’ That’s my favorite thing to do here.” (MD)

How much you can change a person: “I do believe that people can change. I’ve seen it. I’ve seen drastic changes in people in my life due to death of a loved one, having a child, and other things that are even smaller like medication. [Laughs] My personal theory is you should never enter an intimate relationship with someone, friendship or otherwise, romantic, with the hope that they will change. Because you’re dead in the water then. You can say, ‘Let’s work on it, and let’s see how we get there,’ but you really shouldn’t bank on it because I do think it’s kinda rare.” (MD)

On allowing Moss to guide the female voice of the highly improvised film: “We invited her into the process, in particular Lizzie, very early on while we were still crafting the outline so that we could get her voice in there. So there was less of her going, ‘That’s not what girls say!’ And more just us asking her questions and talking to her. I’m not sure how much that was a male/female divide as much as it was just a Lizzie Moss divide.” (MD)

If McDowell thought he was taking on a particularly challenging film for his first feature: “Yeah, sort of, but I didn’t let myself really think about it. I think it scared the crap out of me, which really excited me. And that for me is the only way I’ll make movies is something that feels terrifying because that just means we’re trying something new and different and we’re kind of pushing the envelope. For me it was less about feeling nervous of how I was going to pull it off, and then just finding solutions of how to pull it off. Making sure everything was shot-listed, storyboarded going into it, making sure we knew what to do with the effects, having visual references, all that, and obviously a lot of the work with talking with actors and figuring out what scenes were and tone. It was just being prepared and making sure that we knew what we were all doing and on the same page.”

Something onscreen that translated into Duplass exploring himself: “I think the only thing that once was really funny for me, I got pretty deep into an improv in the first scene I did with Rosemarie DeWitt in ‘Your Sister’s Sister.’ And we shot it a couple times to get it right. And a lot of me came out in that scene while we were doing it. It happens when you get deep in an improv. And then a couple scenes later she’s describing my character to Emily Blunt’s. She’s like, ‘What’d you think of him?’ She’s like, ‘He was all right. He’s a little full of himself, but I kinda liked him.’ I remember being like, ‘Why would she say that?’ And I started thinking about it and started thinking about myself in that scene, and I was like, ‘[Bleep], she’s right!’ I think I was doing some of this false modesty stuff, and she totally called me on it. I was like, ‘All right, that’s good. I learned something. Rosemarie DeWitt’s really smart.’”

And just like that, there’s only one day left of Lolla. Here’s what stood out to us from day 2. Best: The Tallest Man on Earth: Maybe it was just a right-mood, right-set situation, but boy this was the perfect mid-day act to take a breather, sit in the sun, and just chill and listen to and enjoy....

One day down! Here’s the best and worst we saw at Lolla on Friday, plus a few superlatives from day 1. Best: Anyone who knows me knows I was bound to pick Paul McCartney as my favorite act of the day. The Beatle came out and gave it his all with more than two hours of hits, tributes and jokes about...